Photoresist composition and method of manufacturing a display substrate using the same

ABSTRACT

A photoresist composition includes an alkali-soluble resin, a dissolution inhibitor including a quinone diazide compound, a first additive including a benzenol compound represented by the following Chemical Formula 1, a second additive including an acrylic copolymer represented by the following Chemical Formula 2 and an organic solvent. Accordingly, heat resistance of a photoresist pattern may be improved, and the photoresist pattern may be readily stripped. As a result, crack formation in the photoresist pattern may be reduced and/or prevented.

This application claims priority to Korean Patent Applications No.2009-101988, filed on Oct. 27, 2009, and all the benefits accruingtherefrom under 35 U.S.C. §119, the contents of which are hereinincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This application relates to a photoresist composition and a method ofmanufacturing a display substrate using the photoresist composition.More particularly, this application relates to a photoresist compositionthat may be used for a display device, and a method of manufacturing adisplay substrate using the photoresist composition.

2. Description of the Related Art

In general, a liquid crystal display (“LCD”) panel includes a displaysubstrate, an opposing substrate facing the display substrate and aliquid crystal layer interposed between the display substrate and theopposing substrate. The display substrate includes a gate pattern, asemiconductor pattern, a source pattern and a pixel electrode, which areformed sequentially on a base substrate. The gate pattern, thesemiconductor pattern, the source pattern and the pixel electrode may beformed by patterning thin-film layers by a photolithography process.

Two different layers that are patterned by using two masks through aconventional method may also be patterned by using a single mask. Forexample, photoresist patterns having different thicknesses are formed ona first thin-film layer and a second thin-film layer, which are in turnsequentially formed. Thereafter, the first and second thin-film layersare patterned by etching, using the photoresist pattern as a mask. Afterpatterning the first thin-film layer, a portion of the photoresistpattern is removed to form a remaining pattern, and the second thin-filmlayer is patterned by using the remaining pattern as a mask. In thisway, the number of masks required may be reduced, thereby reducing thecost associated with the expense of using multiple masks.

However, when the second thin-film layer is patterned using theremaining pattern as a mask, the remaining pattern can be damaged by theetchant used to pattern the second thin-film layer, or may undergoreflow and thus loss of resolution or pattern collapse. As a result, thesecond thin-film layer may be more highly etched when compared to thefirst thin-film layer so that the first thin-film layer has a shapewhich protrudes through the second thin-film layer. When the secondthin-film layer is a source metal layer and the first thin-film layer isa silicon layer, the second thin-film layer which substantially servesas an electrode or a signal line may have a smaller size than the firstthin-film layer. Thus, the ratio of the sizes of openings in a displaysubstrate may be reduced.

Accordingly, a photoresist pattern needs to have a high heat resistancein order to form a fine photoresist pattern. Furthermore, it is requiredthat no cracks are generated at the surface of the photoresist patternat a low temperature or by a chemical material, and that the photoresistpattern be readily removed by a stripper. However, when heat resistanceof a photoresist pattern is enhanced, the photoresist pattern may not bereadily removed by a stripper. Furthermore, when the manufacturing(processing) temperature is reduced so as to remove a photoresistpattern easily, cracks may be generated. Thus, there increasing need todevelop a photoresist composition capable of solving those problems.

BRIEF SUMMARY OF THE INVENTION

In an embodiment, a photoresist composition capable of improving areliability of a photoresist pattern is provided.

In another embodiment, a method of manufacturing a display substrateusing the above-mentioned photoresist composition is provided.

A photoresist composition. according to an exemplary embodiment,includes an alkali-soluble resin, a dissolution inhibitor including aquinone diazide compound, a first additive including a benzenol compoundrepresented by the following Chemical Formula 1, a second additiveincluding an acrylic copolymer represented by the following ChemicalFormula 2, and an organic solvent.

In Chemical Formulas 1 and 2, R₁, R₂ and R₃ each independentlyrepresents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms,or a hydroxyalkyl group having 1 to 10 carbon atoms; at least one of R₁,R₂ and R₃ represents a hydroxy group, and R₄, R₅ and R₆ eachindependently represents a hydrogen atom or an alkyl group having 1 to 3carbon atoms; R₇ represents a hydrocarbon having 1 to 6 carbon atoms, ofwhich at least one hydrogen atom is replaceable with a substituent, andR₈ represents a benzyl group or a phenyl group, and m, n, and k are eachindependently an integer of 1 to 99 in which the sum of m, n and k is100.

The alkali-soluble resin may include a fractionated novolac resin.

A glass transition temperature of the fractionated novolac resin may beabout 120° C. to about 150° C.

A weight average molecular weight of the fractionated novolac resin maybe about 20,000 to about 30,000 g/mol.

The photoresist composition includes about 10% to about 25% by weight ofthe alkali-soluble resin, about 1% to about 10% by weight of thedissolution inhibitor, about 0.1% to about 10% by weight of the firstadditive, about 0.1% to about 10% by weight of the second additive and abalance of the solvent. The photoresist composition includes analkali-soluble resin, a dissolution inhibitor including a quinonediazide compound, a first additive including a benzenol compoundrepresented by the Chemical Formula 1, a second additive including anacrylic copolymer represented by the Chemical Formula 2 and an organicsolvent. The source metal layer is patterned by with the photoresistpattern as an etching mask to form a source pattern and an activepattern. The source pattern includes a data line, a source electrode anda drain electrode. The active pattern is formed under the source anddrain electrodes, and a pixel electrode electrically connected to thedrain electrode is formed on the base substrate having the sourcepattern and the active pattern

According to another embodiment, there is provided a method ofmanufacturing a display substrate. In the method, a gate patternincluding a gate line and a gate electrode is sequentially formed on asurface of a base substrate to form a multilayer stack. A gateinsulation layer, a semiconductor layer, an ohmic contact layer and asource metal layer are thus sequentially formed on a surface of the basesubstrate having the gate pattern to form the multilayer stack. Aphotoresist composition is coated on the surface of the base substratehaving the source metal layer to form a photoresist pattern.

The photoresist pattern may include a first thickness portion having afirst thickness and overlapping with the source pattern, and a secondthickness portion having a second thickness smaller the first thicknessand overlapping with a gap between the source electrode and the drainelectrode.

The photoresist pattern may be heated at a temperature of about 140° C.to about 150° C. A shape of the photoresist pattern prior to heating maybe substantially the same as a shape of the photoresist pattern afterheating.

In another embodiment, a heat resistance of a photoresist pattern may beimproved, and the photoresist pattern may be readily stripped.Furthermore, crack formation in the photoresist pattern may be reducedand/or prevented.

In another embodiment, a method of forming a pattern using thephotoresist composition may include forming a photoresist film on asubstrate to be patterned from the photoresist composition, exposing thephotoresist film, developing the exposed photoresist film to form apatterned photoresist, and etching the substrate to form a pattern. Thepatterned photoresist prepared from the photoresist composition does notexhibit crack formation at a processing temperature of less than about120° C. or in the presence of an etching solution.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detailed exemplaryembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a cross sectional view illustrating a display device accordingto an exemplary embodiment;

FIG. 2 is a cross-sectional view illustrating an exemplary displaydevice;

FIGS. 3, 4 and 5 are cross-sectional views illustrating a method ofmanufacturing the exemplary display device illustrated in FIG. 2;

FIG. 6 is a cross-sectional view illustrating a display device accordingto another exemplary embodiment; and

FIG. 7 is a cross-sectional view illustrating a display device accordingto still another exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments are described more fully hereinafter with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. The invention may, however, be embodied in manydifferent forms and should not be construed as limited to the exemplaryembodiments set fourth herein. Rather, these exemplary embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the present invention to those skilled in theart. In the drawings, the sizes and relative sizes of layers and regionsmay be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or connected to the other element or layer or interveningelements or layers may be present. In contrast, when an element isreferred to as being “directly on” or “directly connected to” anotherelement or layer, the elements are in at least partial contact with eachother and there are no intervening elements or layers present. Likenumerals refer to like elements throughout. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

It will be understood that, although the terms first, second, third, andthe like may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings herein.

Spatially relative terms, such as “lower,” “upper” and the like, may beused herein for ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. It will be understood that the spatially relative terms areintended to encompass different orientations of the apparatus in use oroperation in addition to the orientation depicted in the figures. Forexample, if the apparatus in the figures is turned over, elementsdescribed as “lower” other elements or features would then be oriented“upper” the other elements or features. Thus, the exemplary term “lower”can encompass both an orientation of above and below. The apparatus maybe otherwise oriented (rotated 90 degrees or at other orientations) andthe spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularexemplary embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Exemplary embodiments of the invention are described herein withreference to cross sectional illustrations that are schematicillustrations of idealized embodiments (and intermediate structures). Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments of the invention should not beconstrued as limited to the particular shapes of regions illustratedherein but are to include deviations in shapes that result, for example,from manufacturing.

For example, an implanted region illustrated as a rectangle will,typically, have rounded or curved features and/or a gradient of implantconcentration at its edges rather than a binary change from implanted tonon implanted region. Likewise, a buried region formed by implantationmay result in some implantation in the region between the buried regionand the surface through which the implantation takes place. Thus, theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the actual shape of a region of anapparatus and are not intended to limit the scope of the presentinvention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. Also herein, the term “about,” where usedto describe the endpoint of a range, will be understood to imply theintrinsic error in determining the range endpoints, and will be limitedto be no greater than currently accepted measurement error according tocapabilities commonly found in the art unless otherwise defined. Forexample, where a compositional range is disclosed, the term “about” maydefine the error intrinsic to measurement of mass using, for example, abalance or load cell as would be routinely used by the skilledpractitioner, or where a temperature range is disclosed, the term“about” may define the error intrinsic to temperature measurements thatwould be routinely used by the skilled practitioner.

All methods described herein can be performed in a suitable order unlessotherwise indicated herein or otherwise clearly contradicted by context.The use of any and all examples, or exemplary language (e.g., “suchas”), is intended merely to better illustrate the invention and does notpose a limitation on the scope of the invention unless otherwiseclaimed. No language in the specification should be construed asindicating any non-claimed element as essential to the practice of theinvention as used herein.

Photoresist Composition

A photoresist composition according to an embodiment includes a) analkali-soluble resin, b) a dissolution inhibitor, c) a first additive,d) a second additive and e) an organic solvent.

(a) Alkali-Soluble Resin

The alkali-soluble resin includes a fractionated novolac resin. Thefractionated novolac resin may be defined as a resin which occupiesmiddle molecular weight region of the molecular weight distribution(referred to sometimes as the “polymer molecular weight distribution”)which is obtained by fractionating a synthesized resin and excluding thepolymeric components forming the high molecular weight region and themonomeric or low molecular weight components forming the low molecularweight region. “Molecular weight region” and “polymer molecular weightdistribution” may refer to either regions or the entirety of the weightaverage molecular weight distribution, or the number average molecularweight distribution, and fractions taken from these distributions.Hereinafter, the “fractionated novolac resin” will refer to a middlemolecular weight fraction based on weight average molecular weight forthe novolac resin, unless otherwise noted.

The fractionated novolac resin is obtained by an addition-condensationreaction of a phenol compound with an aldehyde compound or a ketonecompound. A condensation product obtained by the addition-condensationreaction is then fractionated and cut to exclude a high molecular weightregion and a low molecular weight region to prepare the fractionatednovolac resin. Examples of methods of fractionating may includeselective washing of the alkali-soluble resin using solvents or solventcombinations in which the alkali-soluble resin is partially soluble,precipitation by dissolving the alkali-soluble resin in a solvent, andprecipitation from a non-solvent miscible with the solvent, and/orpreparative scale size exclusion chromatography in which the desiredmolecular weight fractions are collected upon elution, combined, and thefractionated polymer isolated by precipitation or removal of the elutionsolvent.

Examples of the phenol compound may include phenol, ortho-cresol,meta-cresol, para-cresol, 2,5-xylenol, 3,5-xylenol, 3,4-xylenol,2,3,4-trimethylphenol, 4-t-butylphenol, 2-t-butylphenol,3-t-butylphenol, 3-ethylphenol, 2-ethylphenol, 4-ethylphenol,3,3-methyl-6-t-butylphenol, 4-methyl-2-t-butylphenol, 2-naphthol,1,3-dihydroxynaphthalene, 1,7-dihydroxynaphthalene,1,5-dihydroxynaphthalene, and the like. These phenol compounds may beused alone or in a combination thereof.

Examples of the aldehyde compound may include formaldehyde,paraformaldehyde, acetaldehyde, propionaldehyde, benzaldehyde,alpha-phenylpropionaldehyde, beta-phenylpropionaldehyde,ortho-hydroxybenzaldehyde (salicylaldehyde), meta-hydroxybenzaldehyde,para-hydroxybenzaldehyde, glutaraldehyde, glyoxal,ortho-methylbenzaldehyde, para-methylbenzaldehyde, and the like. Thesealdehyde compounds may be used alone or in a combination thereof.

Examples of the ketone compound may include acetone, methylethylketone,diethylketone, methyphenylketone (acetophenone), diphenylketone, and thelike. These may be used each alone or in a combination thereof.

The addition-condensation reaction of a phenol compound with an aldehydecompound or a ketone compound may be performed in the presence of anacid catalyst. For example, the addition-condensation reaction may beperformed at a temperature of about 60° C. to about 250° C. for about 2hours to about 30 hours. Examples of the acid catalyst may include anorganic acid such as oxalic acid, formic acid, trichloroacetic acid,para-toluenesulfonic acid and the like, an inorganic acid such ashydrochloric acid, sulfuric acid, perchloric acid, phosphoric acid, andthe like, and a bivalent metal salt such as acetic acid zinc salt,acetic acid magnesium salt, and the like. Combinations of these acidcatalysts may also be used.

When the weight average molecular weight of the fractionated novolacresin is less than 20,000 g/mol, the fractionated novolac resin may betoo readily dissolved by an alkali solution of developer, therebycausing damage to the pattern being formed such as undercut, loss ofprofile/rounding, or other artifacts. When a weight average molecularweight of the fractionated novolac resin is more than 30,000 g/mol, thedifference in solubility of a photoresist film between an exposed regionand a non-exposed region is reduced so that contrast is reduced, andhigher resolution fine photoresist patterns do not form cleanly. Thus,the weight average molecular weight of the fractionated novolac resinmay be about 20,000 to about 30,000 g/mol, specifically about 21,000 toabout 29,000 g/mol, and still more specifically about 22,500 to about27,500 g/mol. The fractionated novolac resin has a narrow polydispersityof less than or equal to about 3, specifically less than or equal toabout 2.5, and more specifically less than or equal to about 2.

The glass transition temperature (T_(g)) of the fractionated novolacresin may be about 120° C. to about 150° C. The T_(g) of thefractionated novolac resin is thus selected such that, a photoresistpattern formed from the photoresist composition and including thefractionated novolac resin does not deform at a thermal processingtemperature of about 120° C. to about 140° C. for the photoresistpattern. Therefore, the photoresist pattern formed from the photoresistcomposition may have a high heat resistance, i.e., resistance to thermaldeformation at a temperature higher than 150° C., thereby preventingdeformation of the photoresist pattern.

When the content of the fractionated novolac resin is less than about10% by weight based on the total weight of the photoresist composition,the heat resistance of a photoresist pattern is reduced so that thephotoresist pattern is readily deformed in a heat-treating process. Whenthe content of the fractionated novolac resin is more than 15% byweight, the photoresist pattern may be resistant to a subsequentstripping process, and cracking of the photoresist pattern may occur.Thus, the content of the fractionated novolac resin may be about 10% toabout 25%, specifically about 12% to about 23%, and still morespecifically about 15% to about 20% by weight, based on the total weightof the photoresist composition.

The alkali-soluble resin may include a single fractionated novolac resinor a combination of different fractionated novolac resins. In anembodiment, a single fractionated resin may be used were, for example,the fractionated novolac resin may be prepared by reacting a phenolcompound including m-cresol and p-cresol in a weight ratio of 40:60 to60:40 with formaldehyde, and fractionating the reaction product. Inanother embodiment where a combination of fractionated novolac resins isused, the alkali-soluble resin may include, for example, a firstfractionated novolac resin and a second fractionated novolac resin. Thefirst fractionated novolac resin may be prepared by reacting a phenolcompound including m-cresol and p-cresol in a weight ratio of 60:40 withformaldehyde and by fractionating the reaction product, and may have aweight average molecular weight of about 20,000 g/mol. The secondfractionated novolac resin may be prepared by reacting a phenol compoundincluding m-cresol and p-cresol in a weight ratio of 50:50 withformaldehyde and by fractionating the reaction product, and may have aweight average molecular weight of about 20,000 g/mol.

(b) Dissolution Inhibitor

The dissolution inhibitor includes a quinone diazide compound. Thedissolution inhibitor may include, for example, a quinone diazidesulfonic acid ester compound, sometimes referred to in the art as adiazonaphthoquinone (“DNQ”) compound. The quinone diazide sulfonic acidester compound may be prepared by a reaction of a phenol compound(sometimes referred to in the art as a “backbone”) having a hydroxylgroup and a quinone diazide sulfonic acid halide compound.

Examples of the phenol compound having a hydroxyl group may include2,3,4-trihydroxybenzophenone, 2,4,6-trihydroxybenzophenone,2,3,4,3′-tetrahydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone,tri(p-hydroxyphenyl)methane, 1,1,1-tri(p-hydroxyphenyl)ethane,4,4′-[1-[4-[1-[4-hydroxyphenyl]-1-methylethyl]phenyl]ethylidene]diphenol,and the like. The phenol compounds may be used alone or in a combinationthereof.

Examples of the quinone diazide sulfonic acid halide compound mayinclude 1,2-naphthoquinonediazide-5-sulfonic acid chloride,1,2-naphthoquinonediazide-4-sulfonic acid chloride,1,2-benzoquinonediazide-4-sulfonic acid chloride, o-quinonediazidesulfonyl chloride, and the like. The quinone diazide sulfonic acidhalide compounds may be used alone or in a combination thereof.

The quinone diazide compound may be prepared by reacting, in anexemplary embodiment, 2,3,4-trihydroxybenzophenone with o-quinonediazidesulfonyl chloride in the presence of a base such as triethylamine andseparating an obtained product through a following process. The molaramounts of phenol compound and quinone diazide sulfonic acid halidecompound may be selected to prepare quinone diazide compounds in whichthe ratio of DNQ to backbone is 1:1 or less based on the number ofhydroxy groups on the backbone; for example, where2,3,4-trihydroxybenzophenone is condensed with o-quinonediazide sulfonylchloride, the molar ratio of these components in the condensed quinonediazide compound is 1:1, 1:2, or 1:3, or an averaged combination ofthese, depending on the charge. In the following process, theintermediate product may react with water to precipitate the isolatedproduct, which may then be collected by filtration and dried to providethe isolated product as a powder, in the solid phase. Alternatively, theintermediate product may be treated with a resist solution or solventsuch as, for example, a solution including 2-heptanone, rinsed withwater, and phase separated, and the solvent removed by distillation orequilibrium flash distillation. As a result, the product may be obtainedin the liquid phase in a resist solution. The equilibrium flashdistillation is a continuous distillation. According to the equilibriumflash distillation, a portion of a liquid mixture is distilled, and avapor obtained thereby makes contact with the liquid. When equilibriumbetween the obtained vapor and the liquid is reached, the liquid andvapor are separated.

When the content of the dissolution inhibitor is less than about 1% byweight based on the total weight of the photoresist composition, thecontent of dissolution inhibitor may be insufficient to preventdissolution of the fractionated novolac resin by the alkali developingsolution. When the content of the dissolution inhibitor is more thanabout 10%, the fractionated novolac resin may not be soluble in thealkali developing solution and may not form a photoresist pattern.Therefore, the content of the dissolution inhibitor may be about 1% toabout 10%, specifically about 2 to about 8%, and still more specificallyabout 3 to about 7% by weight based on the total weight of thephotoresist composition.

(c) First Additive

The first additive includes a benzenol compound represented by thefollowing Chemical Formula 1.

In Chemical Formula 1, R₁, R₂ and R₃ each independently represent ahydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkylhydroxyl group having 1 to 10 carbon atoms, where at least one of R₁, R₂and R₃ represents a hydroxyl group. The alkyl group may be a linear orbranched alkyl group. Exemplary alkyl groups include methyl, ethyl,n-propyl, isopropyl, 1- or 2-butyl, isobutyl, t-butyl, 1-, 2-, or3-pentyl, 1,1- or 2,2-dimethylpropyl, 2-methylbutyl, 3-methylbutyl, 1-,2-, 3-hexyl, 1,1-, 2,2-, or 3,3-dimethylbutyl, 1,2-, 1,3-, or2,3-dimethylbutyl, 2-methylbutyl, 3-methylbutyl, n-octyl, 3-octyl,1,1,3,3-tetramethylbutyl, n-decyl, cyclopentyl, 1-methylcyclopentyl,cyclohexyl, 2-methoxyethyl, 2-ethoxyethyl, 2-methoxypropyl,2-ethoxypropyl, or the like. Combinations of these groups may be used.Additionally, the alkyl hydroxyl group may be a linear or branchedhydroxyalkyl group. Exemplary hydroxyalkyl groups may include2-hydroxyethyl, 2-hydroxypropyl, 2,3-dihydroxypropyl, 2-hydroxybutyl,4-hydroxybutyl, 2,3-dihydroxybutyl, 2-hydroxypentyl, 2-hydroxyhexyl,hydroxycyclohexyl, methylhydroxycyclohexyl, 2,3- or 2,4-dihydroxymethyl,hydroxymethylcyclohexyl, inosityl, 2-(2-hydroxyethoxy)ethyl,2-(2-(2-hydroxyethoxy)ethoxy)ethyl, and the like. Combinations of thesegroups may be used.

The first additive enhances the interaction between the fractionatednovolac resin and the alkali developing solution capable of dissolvingthe fractionated novolac resin. While not wishing to be bound by theory,it is believed that this enhancement occurs because of the interactionby hydrogen bonding of compatible functional groups (e.g., phenolichydroxy groups) present on the fractionated novolac and the firstadditive, which may reduce the pKa of some of the base-soluble phenolhydroxy groups on the fractionated novolac and thereby enhance basesolubility of the fractionated novolac. Further, a stripping solutionthat is hydrophilic may readily penetrate between the photoresistpattern and a lower layer formed under the photoresist pattern. Thus,the photoresist pattern formed from the photoresist composition may bereadily stripped.

When a content of the first additive is less than 0.1% by weight basedon the total weight of the photoresist composition, the interactionbetween the fractionated novolac resin and the alkali developingsolution may not occur and dissolution in alkali developer solution maynot be enhanced. Thus, the photoresist pattern may not be sufficientlyremoved to clear the pattern. When a content of the first additive ismore than 10% by weight, the heat resistance of the photoresist patternmay be reduced. Thus, a content of the first additive the may be about0.1% to about 10%, and specifically about 0.1% to about 5% by weightbased on the total weight of the photoresist composition.

(d) Second Additive

The second additive includes an acryl copolymer represented by thefollowing Chemical Formula 2.

In Chemical Formula 2, R₄, R₅ and R₆ each independently represents ahydrogen atom or an alkyl group having 1 to 3 carbon atoms, R₇represents a hydrocarbon having 1 to 6 carbon atoms, of which at leastone hydrogen atom is replaceable by a substituent, R₈ represents asubstituted or unsubstituted benzyl group or phenyl group, and m, n, andk independently represent an integer of 1 to 99 such that the sum of m,n and k is 100. Exemplary alkyl groups having 1 to 3 carbon atoms for R₄to R₆ include methyl, ethyl, n-propyl, isopropyl, 2-methoxyethyl, or thelike, or a combination of these. Exemplary alkyl groups having 1 to 6carbon atoms for R₇ include methyl, ethyl, n-propyl, isopropyl, f- or2-butyl, isobutyl, t-butyl, 1-, 2-, or 3-pentyl, 1,1- or2,2-dimethylpropyl, 2-methylbutyl, 3-methylbutyl, 1-, 2-, 3-hexyl, 1,1-,2,2-, or 3,3-dimethylbutyl, 1,2-, 1,3-, or 2,3-dimethylbutyl,2-methylbutyl, 3-methylbutyl, cyclopentyl, 1-methylcyclopentyl,cyclohexyl, 1-methylcyclohexyl, 2-methoxyethyl, 2-ethoxyethyl,2-methoxypropyl, 2-ethoxypropyl, or the like, or a combination of these.The hydrogen atom of the hydrocarbon replaceable in R₇ may besubstituted for an alkyl group, and specifically an alkyl group having 1to 10 carbon atoms, a hydroxyalkyl group, and specifically ahydroxyalkyl group having 1 to 10 carbon atoms, a alkoxy group andspecifically an alkoxy group having 1 to 10 carbon atoms, or acycloalkyl group having 3 to 6 carbon atoms, including both cycloalkyland heterocycloalkyl groups including a heteroatom such as oxygen,nitrogen, silicon, or the like.

While not wishing to be bound by theory, the second additive mayminimize the inner stress of a photoresist pattern, which may in turn becaused by diffusion into the photoresist pattern of an etching solution,including nitric acid of high concentration for etching a lower layerformed under the photoresist pattern, thereby preventing crack formationat the surface of the photoresist pattern. Furthermore, the secondadditive may prevent crack formation at low temperature, for example, ata temperature less than about 120° C., from the use of fractionatednovolac resin. Thus in an embodiment, the patterned photoresist does notexhibit crack formation at a processing temperature of less than about120° C. or in the presence of an etching solution.

The second additive may be prepared by copolymerization of anunsaturated carboxylic acid and a radical polymerizing compound (i.e., acomonomer). Examples of the unsaturated carboxylic acids includemethacrylic acid, acrylic acid, itaconic acid, maleic acid, and thelike. Combinations of these unsaturated carboxylic acids may be used.Examples of the radical polymerizing compound may includemethyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate,n-butyl(meth)acrylate, pentyl(meth)acrylate, benzyl(meth)acrylate,2-methoxyethyl(meth)acrylate, methoxytriethyleneglycol(meth)acrylate,3-methoxybutyl(meth)acrylate, ethylcarbitol(meth)acrylate,phenoxypolyethyleneglycol(meth)acrylate, and the like. These radicalpolymerizing compounds may be used alone or in a combination thereof.

When the content of the second additive is less than about 0.1% byweight of the total weight of the photoresist composition, cracks mayform in the photoresist pattern during application of external heatand/or external chemical material. When the content of the secondadditive is more than about 10% by weight, the sensitivity of thephotoresist composition may be reduced. Thus, the content of the secondadditive may be about 0.1% to about 10%, specifically about 0.5 to about9% by weight based on the total weight of the photoresist composition.

When the weight average molecular weight of the second additive is lessthan about 5,000 g/mol, cracking may not be prevented. When a weightaverage molecular weight of the second additive is more than about10,000 g/mol, the sensitivity of the photoresist composition may bereduced and the resolution may therefore decrease. Thus, a weightaverage molecular weight of the second additive may be about 5,000 toabout 10,000 g/mol, specifically about 6,000 to about 9,000 g/mol.

(e) Organic Solvent

The organic solvents useful herein may include ethers, glycol ethers,ethylene glycol alkyl ether acetates, diethylene glycols, propyleneglycol monoalkyl ethers, aromatic hydrocarbons, ketones, esters, and thelike. These may be used each alone or in a combination thereof.Exemplary organic solvents may include ethyl lactate, 2-heptanone,cyclohexanone, anisole, propylene glycol methyl ether, propylene glycolethyl ether, propylene glycol methyl ether acetate (PGMEA), diethyleneglycol monomethyl ether, diethylene glycol monomethyl ether acetate,dipropylene glycol monomethyl ether, dipropylene glycol monomethyl etheracetate, butyl acetate, pentyl acetate, ethoxyethylpropionate, or thelike, and combinations thereof.

(f) Others

The photoresist composition may further include a surfactant, anadhesion promoter, and the like added to the alkali-soluble resin, thedissolution inhibitor, the first additive, the second additive and theorganic solvent. Contents of the surfactant and the adhesion promotermay be determined depending on contents of the alkali-soluble resin, thedissolution inhibitor, the first additive and the second additive.However, a content of each of the surfactant and the adhesion promotermay be preferably about 0% to about 1% by weight so as not to affectreactions of the alkali-soluble resin, the dissolution inhibitor, thefirst additive and the second additive.

The surfactant may improve a coating ability or a developing ability ofa photoresist composition. Examples of the surfactant may include polyoxyethyleneothylphenyl ether, poly oxyethylenenonylphenyl ether;surfactants marketed under the trade names F171, F172, and F173 by DAINIPPON INK; fluorinated surfactants marketed under the tradenames FC430and FC431 by SUMITOMO 3M; KP341 surfactant available from SINWOLCHEMICAL INDUSTRY, and the like. These surfactants may be used alone orin a combination thereof.

The adhesion promoter may improve adhesion between a photoresist patternand a lower layer. Examples of the adhesion promoter may include asilane coupling agent having a reactive substitution group such as acarboxylic group, a methacrylic group, an isocyanate group, and an epoxygroup. Examples of a silane coupling agent may includegamma-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane,vinyltrimethoxysilane, gamma-isocyanatopropyltriethoxysilane,beta-3,4-epoxy cyclo hexylethyltrimethoxysilane, and the like. Theseadhesion promoters may be used alone or in a combination thereof.

The viscosity of the photoresist composition may be about 3 cP(centipoise) to about 15 cP. The photoresist composition may patterned.In an embodiment, a method of forming a pattern using the photoresistcomposition may include forming a photoresist film on a substrate to bepatterned from the photoresist composition, exposing the photoresistfilm with an actinic radiation, such as, for example, UV radiationincluding g-line, i-line, or other radiation, developing the exposedphotoresist film to form a patterned photoresist, and etching thesubstrate to form a pattern. The developer may desirably be an aqueousbasic developer. By use of the photoresist composition disclosed herein,the patterned photoresist prepared from the photoresist composition doesnot exhibit crack formation at a processing temperature of less thanabout 120° C. or in the presence of an etching solution.

Hereinafter, the photoresist composition and use thereof will bedescribed with reference to specific examples and comparative examples.

Example 1

(a-1) About 12% by weight of a first fractionated novolac resin having aweight average molecular weight of about 20,000 g/mol and prepared byreacting a phenol mixture including m-cresol and p-cresol in a weightratio of about 60:40 with formaldehyde and fractionating an obtainedproduct by, (a-2) about 8% by weight of a second fractionated novolacresin having a weight average molecular weight of about 20,000 g/mol andprepared by reacting a phenol mixture including m-cresol and p-cresol ina weight ratio of about 50:50 with formaldehyde and fractionating anobtained product by, (b) about 7% by weight of a quinone diazidecompound prepared by reacting2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5-dimethylbenzyl]-4-methylphenolwith 1,2-naphthoquinonediazide-5-sulfonic acid chloride in a mole ratioof about 1:2.2, (c) about 0.5% by weight of 1,3-dihydrobenzene, (d)about 0.5% by weight of SPCY-series polymer (trade name, SHOWA POLYMER)having a weight average molecular weight of about 8,000 as an acryliccopolymer, (e) about 36.5% by weight of propylene glycol methyl etheracetate (PGMEA) as an organic solvent and about 35.5% by weight of ethyllactate (EL) were mixed, and filtered through a fluorine resin filter toprepare a photoresist composition having a viscosity of about 15 cP. Aglass transition temperature of the first and second fractionatednovolac resins was about 120° C.

Example 2

(a-1) About 12% by weight of a first fractionated novolac resin having aweight average molecular weight of about 20,000 g/mol and prepared byreacting a phenol mixture including m-cresol and p-cresol in a weightratio of about 60:40 with formaldehyde and fractionating an obtainedproduct by, (a-2) about 8% by weight of a second fractionated novolacresin having a weight average molecular weight of about 20,000 g/mol andprepared by reacting a phenol mixture including m-cresol and p-cresol ina weight ratio of about 50:50 with formaldehyde and fractionating anobtained product by, (b) about 7% by weight of a quinone diazidecompound prepared by reacting2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5-dimethylbenzyl]-4-methylphenolwith 1,2-naphthoquinonediazide-5-sulfonic acid chloride in a mole ratioof about 1:2.2, (c) about 0.5% by weight of 1,2,3-trihydrobenzenepyrogallic acid, (d) about 0.5% by weight of SPCY-series polymer (tradename, SHOWA POLYMER) having a weight average molecular weight of about8,000 as an acrylic copolymer, (e) about 36.5% by weight of propyleneglycol methyl ether acetate (PGMEA) as an organic solvent and about35.5% by weight of ethyl lactate (EL) were mixed, and filtered through afluorine resin filter to prepare a photoresist composition having aviscosity of about 15 cP. A glass transition temperature of the firstand second fractionated novolac resins was about 120° C.

Comparative Examples 1 to 6

Comparative photoresist compositions of Comparative Examples 1 to 6 wereprepared according to the following Table 1.

TABLE 1 Dissolution First Second Resin inhibitor additive additiveSolvent (content) (content) (content) (content) (content) ComparativeExample 1 A-1/A-2 B (7) — — E/F(36.5/36.5) (12/8) Comparative Example 2A-1/A-2 B (7) C-1 (0.5) E/F(36.3/36.2) (12/8) Comparative Example 3A-1/A-2 B (7) C-2 (0.5) E/F(36.3/36.2) (12/8) Comparative Example 4A-1/A-2 B (7) D-1 (0.5) E/F(36.3/36.2) (12/8) Comparative Example 5A-1/A-2 B (7) D-2 (0.5) E/F(36.3/36.2) (12/8) Comparative Example 6A-3/A-4 B (7) — — E/F(36.5/36.5) (12/8)

A-1: a first fractionated novolac resin having a weight averagemolecular weight of about 20,000 g/mol and a glass transitiontemperature of about 120° C., and prepared by reacting a phenol mixtureincluding m-cresol and p-cresol in a weight ratio of about 60:40 withformaldehyde and fractionating an obtained product by;

A-2: a second fractionated novolac resin having a weight averagemolecular weight of about 20,000 and a glass transition temperature ofabout 120° C., and prepared by reacting a phenol mixture includingm-cresol and p-cresol in a weight ratio of about 50:50 with formaldehydeand fractionating an obtained product by;

A-3: a third fractionated novolac resin having a weight averagemolecular weight of about 16,000 and a glass transition temperature ofabout 100° C., and prepared by reacting a phenol mixture includingm-cresol and p-cresol in a weight ratio of about 60:40 with formaldehydeand fractionating an obtained product by;

A-4: a fourth fractionated novolac resin having a weight averagemolecular weight of about 15,000 and a glass transition temperature ofabout 100° C., and prepared by reacting a phenol mixture includingm-cresol and p-cresol in a weight ratio of about 50:50 with formaldehydeand fractionating an obtained product by;

B: a quinone diazide compound prepared by reacting2,6-bis[4-hydroxy-3-(2-hydroxy-5-methylbenzyl)-2,5-dimethylbenzyl]-4-methylphenolwith 1,2-naphthoquinonediazide-5-sulfonic acid chloride in a mole ratioof about 1:2.2;

C-1: 1,3-hydrobenzene;

C-2: 1,2,3-trihydrobenzene pyrogallic acid;

D-1: SPCY-series polymer (trade name, SHOWA POLYMER) having a weightaverage molecular weight of about 8,000 g/mol as an acrylic copolymer;

D-2: SPCY-series polymer (trade name, SHOWA POLYMER) having a weightaverage molecular weight of about 20,000 g/mol as an acrylic copolymer;

E: propylene glycol methyl ether acetate (PGMEA); and

F: ethyl lactate (EL).

Forming a Photoresist Pattern

Each of photoresist compositions of Examples 1 and 2 and ComparativeExamples 1 to 6 was spin-coated on a silicon wafer treated withhexamethyldisilazane, and pre-baked on a hot plate at a temperature ofabout 90° C. for about 60 seconds to form a photoresist film having athickness of about 1.50 μm. The silicon wafer having the photoresistfilm was exposed to light using an NSR-2005 i9C i-Line stepper (NikonCo. Ltd., NA=0.57, σ=0.60), at incrementally different exposure doses.Thereafter, the exposed photoresist film was heated at a temperature ofabout 110° C. for about 60 seconds, and then developed bytetramethylammonium hydroxide having a concentration of about 2.38 wt %for about 60 seconds to form a photoresist pattern.

Evaluation of a Photoresist Pattern

(1) Evaluation of Crack Resistance

T-01 stripper (trade name, DONGWOO FINECHEM, Korea) was applied to thephotoresist pattern formed from each of the photoresist compositions ofExamples 1 and 2 and Comparative Examples 1 to 6, and crack formation onthe surface of the photoresist pattern was observed. The resultsobtained are represented by “Very good” (⊚), “Good” (∘), “Normal” (Δ)and “Poor” (x) in the following Table 2.

(2) Evaluation of Stripping

PRS-2000 stripper (DONGWOO FINECHEM, Korea) was applied to thephotoresist pattern formed from each of the photoresist compositions ofExamples 1 and 2 and Comparative Examples 1 to 6 to strip thephotoresist pattern, and a surface of the silicon wafer was observed.The results obtained are represented by “Very good” (⊚), “Good” (∘),“Normal” (Δ) and “Poor” (x) in the following Table 2.

(3) Evaluation of Heat Resistance

The photoresist pattern formed from each of the photoresist compositionsof Examples 1 and 2 and Comparative Examples 1 to 6 to strip thephotoresist pattern was heated at a temperature of about 150° C. forabout 150 seconds, and the profile of the photoresist pattern wasobserved by a scanning electron microscopy (“SEM”). The results obtainedare represented by “No deformation” (⊚), “Small deformation” (∘),“Normal deformation” (Δ) and “Large deformation” (x) in the followingTable 2.

TABLE 2 Crack resistance Stripping Heat resistance Example 1 ◯ ◯ ⊚Example 2 ◯ ◯ ⊚ Comparative Example 1 X X ⊚ Comparative Example 2 X ◯ ⊚Comparative Example 3 X ◯ ⊚ Comparative Example 4 ◯ X ⊚ ComparativeExample 5 X X ⊚ Comparative Example 6 ◯ ◯ X

Referring to Table 2, it can be noted that the photoresist patternsformed from the photoresist compositions according to Examples 1 and 2have relatively better crack-resistance and stripping ability whencompared to the photoresist pattern formed from the photoresistcompositions according to Comparative Examples 1 to 6. Furthermore, itcan be seen that the photoresist patterns formed from the photoresistcompositions according to Examples 1 and 2 are not deformed at atemperature of about 150° C. because the photoresist compositionsinclude fractionated novolac resins having a glass transitiontemperature of about 120° C.

Method of Manufacturing a Display Substrate

Hereinafter, a method of manufacturing a display substrate according toan exemplary embodiment of the present invention will be described withreference to FIGS. 1 to 7.

Referring to FIG. 1, a gate metal layer and a first photoresist pattern210 are formed on a surface of base substrate 110. The gate metal layeris patterned by using the first photoresist pattern 210 as an etchingmask to form a gate pattern including a gate line 121 and a gateelectrode 123, which as illustrated are features forming opposite endsof the same gate metal layer after patterning. The gate metal layer mayhave a double-layered structure including an aluminum layer and amolybdenum layer (not shown).

Referring to FIG. 2, a gate insulation layer 130 is formed on a surfaceof the base substrate 110, a semiconductor layer 140 a is formed on asurface of gate insulation layer 130 opposite base substrate 110, anohmic contact layer 140 b is formed on a surface of semiconductor layer140 a opposite gate insulation layer 130, and a source metal layer 150is formed on a surface of ohmic contact layer 140 b oppositesemiconductor layer 140 a. In this way, each layer is formedsequentially perpendicular to the plane of and on the surface of thebase substrate 110 having the gate pattern to form a multilayer stack.The source metal layer 150 may have a triple-layered structure includinga first metal layer M1 including molybdenum, a second metal layer M2including aluminum and a third metal layer M3 including molybdenum.

A second photoresist pattern 220 is formed on the base substrate 110having the source metal pattern 150. For example, a positive-typephotoresist composition including about 10% to about 25% by weight of analkali-soluble resin, about 1% to about 10% by weight of a dissolutioninhibitor including a quinone diazide compound, about 0.1% to about 10%by weight of a first additive including a benzenol compound representedby the following Chemical Formula 1, about 0.1% to about 10% by weightof a second additive including an acrylic copolymer represented by thefollowing Chemical Formula 2 and a balance of an organic solvent iscoated on the surface of a source metal pattern on the surface of basesubstrate 110 to form a photoresist film. The photoresist film isexposed to light through a mask 200, and then developed to form thesecond photoresist pattern 220.

In Chemical Formula 1, R₁, R₂ and R₃ independently represent a hydrogenatom, an alkyl group having 1 to 10 carbon atoms, or an alkyl hydroxylgroup having 1 to 10 carbon atoms, and at least one of R₁, R₂ and R₃represents a hydroxyl group. In Chemical Formula 2, R₄, R₅ and R₆ eachindependently represent a hydrogen atom or an alkyl group having 1 to 3carbon atoms, R₇ represents a hydrocarbon having 1 to 6 carbon atoms, ofwhich at least one hydrogen atom is replaceable by a substituent, R₈represents a benzyl group or a phenyl group, and m, n, and kindependently represent an integer of 1 to 99 such that the sum of m, nand k is 100. The hydrogen atom of the hydrocarbon maybe replaceablewith an alkyl group, a hydroxyalkyl group, an alkoxy group, or acycloalkyl group having 3 to 6 carbon atoms.

The mask 200, shown in FIG. 2, includes a light-blocking portion 310, ahalf-light-transmitting portion 320 and a light-transmitting portion330. The photoresist film corresponding to the light-blocking portion310 is not removed by a developing solution, and has a first thicknessd1 on the source metal layer 150. The first thickness d1 may besubstantially the same as an initial thickness of the photoresist film.As used herein, “substantially the same” with respect to photoresistfilm thickness means having a thickness, after developing, that issimilar to and comparable with that of the photoresist film beforedeveloping, differing only in ordinary thickness loss intrinsic to thephotoresist film. The photoresist film corresponding to thehalf-light-transmitting portion 320 is partially removed by thedeveloping solution so that a portion of the photoresist filmcorresponding to the half-light-transmitting portion 320 has a secondthickness d2 on the source metal layer 150. The second thickness d2 issmaller than the first thickness d1. The portion of the photoresist filmcorresponding to and exposed through the light-transmitting portion 330of mask 300 is fully removed by the developing solution to expose acorresponding portion of source metal layer 150. As a result, the secondphotoresist pattern 220 is formed to have a first thickness portion TH1having the first thickness d1 and a second thickness portion TH2 havingthe second thickness d2. The first thickness portion TH1 is disposedwhere a source pattern is formed through a following process. Thephotoresist composition has a high photosensitivity. Thus, the firstthickness portion TH1 and the second thickness portion TH2 may be stablyformed.

The base substrate 110 having the second photoresist pattern 220 may beheated after the second photoresist pattern 220 is formed. As a result,adhesion between the second photoresist pattern 220 and the source metallayer 150 may be enhanced. The base substrate 110 may be heated at atemperature of about 140° C. to about 150° C. The second photoresistpattern 220 formed from the photoresist composition is not deformedwhile the second photoresist pattern 220 is heated. Furthermore, anangle θ formed by an upper surface of the base substrate 110 and a sidesurface of the second photoresist pattern 220 is not substantiallychanged when compared to an initial angle after the second photoresistpattern 220 is heated. For example, difference of the angle θ betweenbefore and after performing the heating process may be about 0° to about15°, specifically about 5° to about 10°. Thus, the shape of the secondphotoresist pattern 220 after heating may be, in this way, substantiallythe same as a shape of the second photoresist pattern 220 beforeheating.

The source metal layer 150 is then etched by using the secondphotoresist pattern 220 as an etching mask as shown in FIG. 3.Thereafter, the exposed ohmic contact layer 140 b and the semiconductorlayer 140 a are also etched to expose gate insulation layer 130. Forexample, the source metal layer 150 may be etched by using an integraletching solution capable of etching all of the first, second and thirdmetal layers M1, M2 and M3. The integral etching solution may includenitric acid. A crack is not formed at the second photoresist pattern 220even where the integral etching solution is used. Furthermore, a shapeof a side surface of the second photoresist pattern 220 may besubstantially the same as a shape of an etched surface of the sourcemetal layer 150.

Hereinafter, the source metal layer 150 having a triple-layeredstructure illustrated in FIGS. 3 to 7 will be described as a singlelayer for ease of description.

Referring to FIG. 3, the source metal layer 150 is patterned so that adata line 152 and a provisional electrode pattern 154 connected to thedata line 152 are formed on the base substrate 110. The data line 152crosses the gate line 121, and the provisional electrode pattern 154 isdisposed on the gate electrode 123 to overlap with the gate electrode123.

Thereafter, the ohmic contact layer 140 b and the semiconductor layer140 a are etched using the provisional electrode pattern 154 and thesecond photoresist pattern 220 as an etching mask. Thus, a provisionalactive pattern 142 is formed under the data line 152, and a line pattern(not shown) is formed under the data line 152. The provisional activepattern 142 includes a semiconductor pattern 142 a and an ohmic contactpattern 142 b.

Referring to FIG. 4, the second thickness portion TH2 of the secondphotoresist pattern 220 is removed to form a remaining pattern 222. Thesecond photoresist pattern 220 is removed by the second thickness d2 sothat the first thickness portion TH1 forms the remaining pattern 222having a third thickness d3. The provisional electrode pattern 154 ispartially exposed through the remaining pattern 222.

Referring to FIG. 5, a portion of the provisional electrode pattern 154is removed by using the remaining pattern 222 as an etching mask to forma source electrode 156 connected to the date line 152 and a drainelectrode 158 spaced apart from the source electrode 156. Thus, a sourcepattern including the data line 152, the source electrode 154 (eachshown as occupying the same layer) and the drain electrode 156 is formedon the base substrate 110.

The provisional electrode pattern for source electrode 154 may bepatterned by the integral etching solution. The remaining pattern 222formed from the photoresist composition is hardly stressed internally orexternally by the integral etching solution. In this way, cracks are notformed in the remaining pattern 222.

Thereafter, the ohmic contact pattern 142 b of the provisional activepattern 142, which is exposed between the source electrode 156 and thedrain electrode 158, is removed. Accordingly, an active pattern 146including the semiconductor pattern 142 a, of which a portion is exposedbetween the source electrode 156 and the drain electrode 158, is formed.

The remaining pattern 222 does not deform, and does not exhibit crackformation even if the processes illustrated in FIGS. 4 and 5 areperformed. Thus, the shape of an etched surface of the source electrode156 and the drain electrode 158 may be substantially the same as that ofthe active pattern 146, as a region “SP” illustrated in FIG. 5(encircled portion). Thus, the active pattern 146 does not protruderelative to the source electrode 156 and the drain electrode 158 in alateral direction. Furthermore, the etched surfaces of the data line 152and the line pattern 144 may be substantially the same as each other.

Referring to FIG. 6, the remaining pattern 222 is removed by a strippingsolution. The remaining pattern 222, which has a high heat resistance,may be readily stripped. Thus, the reliability of a process for formingthe source pattern may be improved.

A passivation layer 160 and a planarizing layer 170 are each formedsequentially on and overlaying the base substrate having a thin-filmtransistor SW including the gate electrode 123, the active patternhaving a channel portion CH, the source electrode 156 and the drainelectrode 158.

Referring to FIG. 7, the passivation layer 160 and the planarizing layer170 are patterned to form a contact hole CNT exposing an end of thedrain electrode 158. In an embodiment (not shown), the planarizing layer170 may be omitted.

Thereafter, an electrode layer is formed on the base substrate 110having the contact hole CNT, and patterned to form a pixel electrode180. The pixel electrode 180 makes contact with the drain electrode 158through the contact hole CNT to be electrically connected to thethin-film transistor SW.

In the exemplary embodiments, a process for forming the contact hole CNTand a process for patterning the electrode layer are performedseparately, however, the process for forming the contact hole CNT andthe process for patterning the electrode layer may be performed by usingthe same mask.

According to exemplary embodiments, heat resistance of a photoresistpattern may be improved, and the photoresist pattern may be readilystripped, by use of the photoresist composition disclosed herein.Furthermore, crack formation in the photoresist pattern prepared usingthe photoresist composition may be reduced and/or prevented. Thus, anactive pattern is prevented from protruding relative to an adjacentsource pattern in a method of manufacturing a thin-film transistor. Themethod of manufacturing the thin-film transistor includes forming theactive pattern and the source pattern by using one same mask.

Although the exemplary embodiments have been described, it is understoodthat the present invention should not be limited to these exemplaryembodiments but various changes and modifications can be made by oneordinary skilled in the art within the spirit and scope of the inventionas hereinafter claimed.

1. A photoresist composition comprising: an alkali-soluble resin; adissolution inhibitor including a quinone diazide compound; a firstadditive including a benzenol compound represented by the followingChemical Formula 1; a second additive including an acrylic copolymerrepresented by the following Chemical Formula 2; and an organic solvent,

wherein, R₁, R₂ and R₃ each independently represent a hydrogen atom, analkyl group having 1 to 10 carbon atoms, or a hydroxyalkyl group having1 to 10 carbon atoms, and at least one of R₁, R₂ and R₃ represents ahydroxy group, R₄, R₅ and R₆ each independently represent a hydrogenatom or an alkyl group having 1 to 3 carbon atoms, R₇ represents ahydrocarbon having 1 to 6 carbon atoms, of which at least one hydrogenatom is replaceable, R₈ represents a substituted or unsubstituted benzylgroup or phenyl group, and m, n, and k are each independently an integerof 1 to 99 wherein the sum of m, n and k is
 100. 2. The photoresistcomposition of claim 1, wherein the alkali-soluble resin comprises afractionated novolac resin.
 3. The photoresist composition of claim 2,wherein a glass transition temperature of the fractionated novolac resinis about 120° C. to about 150° C.
 4. The photoresist composition ofclaim 2, wherein a weight average molecular weight of the fractionatednovolac resin is about 20,000 to about 30,000 g/mol.
 5. The photoresistcomposition of claim 1, wherein the dissolution inhibitor includes asulfonic acid ester compound prepared by reaction of a phenol compoundhaving at least one hydroxy group and a quinone diazide sulfonic acidhalide compound.
 6. The photoresist composition of claim 1, wherein aweight average molecular weight of the second additive is about 5,000 toabout 10,000 g/mol.
 7. The photoresist composition of claim 1, whereinthe second additive is prepared by copolymerizing an unsaturatedcarboxylic acid with at least one selected from the group consisting ofmethyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate,n-butyl(meth)acrylate, pentyl(meth)acrylate, benzyl(meth)acrylate,2-methoxyethyl(meth)acrylate, methoxytriethyleneglycol(meth) acrylate,3-methoxybutyl(meth)acrylate, ethylcarbitol(meth) acrylate, andphenoxypolyethyleneglycol(meth)acrylate.
 8. The photoresist compositionof claim 1, wherein the alkali-soluble resin comprises: a firstfractionated novolac resin prepared from a phenol mixture includingm-cresol and p-cresol in a weight ratio of about 60:40; and a secondfractionated novolac resin prepared from a phenol mixture includingm-cresol and p-cresol in a weight ratio of about 50:50.
 9. Thephotoresist composition of claim 1, comprising about 10% to about 25% byweight of the alkali-soluble resin, about 1% to about 10% by weight ofthe dissolution inhibitor, about 0.1% to about 10% by weight of thefirst additive, about 0.1% to about 10% by weight of the second additiveand a balance of the organic solvent.
 10. A method of manufacturing adisplay substrate, the method comprising: forming a gate pattern on asurface of a base substrate, the gate pattern including a gate line anda gate electrode; sequentially forming a gate insulation layer, asemiconductor layer, an ohmic contact layer and a source metal layer onthe base substrate having the gate pattern to form a multilayer stack;coating a photoresist composition on the base substrate having thesource metal layer to form a photoresist pattern, the photoresistcomposition including an alkali-soluble resin, a dissolution inhibitorincluding a quinone diazide compound, a first additive including abenzenol compound represented by the following Chemical Formula 1, asecond additive including an acrylic copolymer represented by thefollowing Chemical Formula 2 and an organic solvent; patterning thesource metal layer having the photoresist pattern as an etching mask toform a source pattern and an active pattern, the source patternincluding a data line, a source electrode and a drain electrode, theactive pattern being formed between the source and drain electrodes andthe base substrate; and forming a pixel electrode electrically connectedto the drain electrode on the base substrate having the source patternand the active pattern,

wherein, R₁, R₂ and R₃ each independently represent a hydrogen atom, analkyl group having 1 to 10 carbon atoms, or a hydroxyalkyl group having1 to 10 carbon atoms, wherein at least one of R₁, R₂ and R₃ represents ahydroxy group, R₄, R₅ and R₆ each independently represent a hydrogenatom or an alkyl group having 1 to 3 carbon atoms, R₇ represents ahydrocarbon having 1 to 6 carbon atoms, of which at least one hydrogenatom is replaceable, R₈ represents a benzyl group or a phenyl group, andm, n, and k are each independently an integer of 1 to 99 wherein the sumof m, n and k is
 100. 11. The method of claim 10, wherein thephotoresist composition comprises about 10% to about 25% by weight ofthe alkali-soluble resin, about 1% to about 10% by weight of thedissolution inhibitor, about 0.1% to about 10% by weight of the firstadditive, about 0.1% to about 10% by weight of the second additive and abalance of the organic solvent.
 12. The method of claim 11, wherein thephotoresist pattern includes a first thickness portion having a firstthickness and overlapping with the source pattern, and a secondthickness portion having a second thickness smaller the first thicknessand overlapping with a gap between the source electrode and the drainelectrode.
 13. The method of claim 12, wherein forming the sourcepattern comprises: etching the source metal layer, the ohmic contactlayer and a semiconductor layer by using the photoresist pattern as anetching mask; removing the second thickness portion of the photoresistpattern; removing an exposed portion of the source metal layer to formthe source electrode and the drain electrode; and forming the activepattern by using the source electrode and the drain electrode as an etchmask.
 14. The method of claim 10, wherein forming the source patterncomprises: etching the ohmic contact layer and a semiconductor layer toform a line pattern disposed between the data line and the basesubstrate.
 15. The method of claim 10, wherein the source metal layercomprises a first metal layer including molybdenum, a second metal layerincluding aluminum and a third metal layer including molybdenum.
 16. Themethod of claim 15, wherein the first, second and third metal layers ofthe source metal layer are each etched by an etching solution includingnitric acid.
 17. The method of claim 10, wherein forming the photoresistpattern comprises: heating the photoresist pattern at a temperature ofabout 140° C. to about 150° C.
 18. The method of claim 17, wherein ashape of the photoresist pattern before heating is substantially thesame as a shape of the photoresist pattern after heating.
 19. A displaysubstrate prepared by the method of claim
 1. 20. A method of forming apattern comprising: forming a photoresist film on a substrate from aphotoresist composition comprising: an alkali-soluble resin comprising afractionated novolac resin, wherein a glass transition temperature ofthe fractionated novolac resin is about 120° C. to about 150° C.; adissolution inhibitor including a quinone diazide compound; a firstadditive including a benzenol compound represented by the followingChemical Formula 1; a second additive including an acrylic copolymerrepresented by the following Chemical Formula 2; and an organic solvent,exposing the photoresist film with i-line radiation, developing theexposed photoresist film to form a patterned photoresist, and etchingthe substrate to form a pattern, wherein the patterned photoresist doesnot exhibit crack formation at a processing temperature of less thanabout 120° C. or in the presence of an etching solution,

wherein, R₁, R₂ and R₃ each independently represent a hydrogen atom, analkyl group having 1 to 10 carbon atoms, or a hydroxyalkyl group having1 to 10 carbon atoms, and at least one of R₁, R₂ and R₃ represents ahydroxy group, R₄, R₅ and R₆ each independently represent a hydrogenatom or an alkyl group having 1 to 3 carbon atoms, R₇ represents ahydrocarbon having 1 to 6 carbon atoms, of which at least one hydrogenatom is replaceable, R₈ represents a substituted or unsubstituted benzylgroup or phenyl group, and m, n, and k are each independently an integerof 1 to 99 wherein the sum of m, n and k is 100.